This invention relates to an apparatus for refining molten metal, and in particular to a new and improved gas distributor for use in such apparatus.
The conventional apparatus for refining molten metal includes a vessel having a heat source, typically electrical resistance heating rods, for heating the metal, and arrangements for placing metal scraps in the vessel and withdrawing molten metal, and arrangements for introducing gas into the molten metal.
The basic concept and the operation of the metal refining apparatus is described in the U.S. Pat. Nos. to Szekely, 3,227,547; 3,743,263; 4,021,026; and 4,040,610.
Gas is pumped into the molten metal in the refining process, and various arrangments have been utilized for distributing the gas through the melt. One such arrangment is shown in the Szekely U.S. Pat. No. 3,743,263 with a rotor positioned below a stator, with the rotor and stator of the same outside diameter and having vanes which when aligned define vertical passages along the stator and rotor outer surfaces. Gas is introduced between the rotor and stator and is directed horizontally outward into the melt. The vaned rotor and stator provide for metal circulation within the melt and for gas distribution.
An alternative configuration for the gas distributor is shown in the U.S. Pat. No. to Pelton, 4,203,581. In this distributor, the stator is smooth and the rotor is vaned, with the rotor extending beyond the stator and with the root diameter of the rotor about the same as the diameter of the stator.
Other variations of the stator-rotor configuration are shown in the aforementioned U.S. Pat. No. to Szekely, 3,227,547 and in the U.S. Pat. No. to Duenkelmann, 4,867,422.
Improved and more efficient refining of the molten metal can be achieved with more uniform and more rapid distribution of the gas throughout the melt. Older designs require a tight control on rotating speed and gap between the stator and impellor in order to maximize shearing of bubbles.